Field
The present invention relates to abnormality detection.
Related Art
JP 2009-201194A discloses a technique of detecting a short-circuit failure of an inverter provided to control a motor generator. This proposed technique detects a short-circuit failure when the current value representing electric current flowing between an arm included in the inverter and the motor generator is greater than a threshold value under the condition that all diode elements constituting the arm are set OFF (gate blocking condition).
The above prior art technique is on the premise that no electric current flows in the inverter by setting the gate blocking condition in the normal state with no occurrence of a short-circuit failure. When the reverse voltage of the motor generator is higher than the system voltage, however, electric current flows in the inverter even in the normal state under the gate blocking condition. Detection of an abnormality based on such electric current leads to erroneous detection. By taking into account the problem of the prior art, an object of the invention is to avoid erroneous detection when the reverse voltage of the motor generator is higher than the system voltage.